import java.util.ArrayList;
import java.util.List;

class TreeNode {
      int val;
      TreeNode left;
      TreeNode right;
      TreeNode() {}
      TreeNode(int val) { this.val = val; }
      TreeNode(int val, TreeNode left, TreeNode right) {
          this.val = val;
          this.left = left;
          this.right = right;
      }
}

public class TestBinaryTree {

    static class TreeNode {
        public char val;
        public TreeNode left;
        public TreeNode right;
        /**
         * 构造方法，构造一个节点
         * @param val
         */
        public TreeNode(char val) {
            this.val = val;
        }
    }

    public TreeNode creteTree() {
        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        TreeNode G = new TreeNode('G');
        TreeNode H = new TreeNode('H');

        A.left = B;
        A.right = C;
        B.left = D;
        B.right = E;
        E.right = H;
        C.left = F;
        C.right = G;
        return A;//根节点
    }


    // 前序遍历
    void preOrder(TreeNode root) {
        if(root == null) {
            return;
        }
        System.out.print(root.val+" ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if(root == null) {
            return;
        }
        inOrder(root.left);
        System.out.print(root.val+" ");
        inOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if(root == null) {
            return;
        }
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val+" ");
    }

    public static int count = 0;
    // 获取树中节点的个数         遍历思路：
    public void size1(TreeNode root){
        if(root == null) {
            return ;
        }
        count++;
        size1(root.right);
        size1(root.left);
    }

    /**
     * 子问题的思路
     * @param root
     * @return
     */
    public int size2(TreeNode root){
        if(root == null) {
            return 0;
        }
        //root不为空
        int tmp = size2(root.left) + size2(root.right)+1;
        return tmp;
    }

    public static int count2 = 0;
    // 获取叶子节点的个数  遍历思路
    void getLeafNodeCount1(TreeNode root){

        if (root == null) {
            return;
        }
        if (root.left == null || root.right == null) {
            count2++;
            return;
        }

        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);

    }

    // 获取 叶子节点的个数  子问题
    int getLeafNodeCount2(TreeNode root){
        if (root == null) {
            return -1;
        }
        if (root.left == null && root.right == null) {
            return 1;
        }
        return getLeafNodeCount2(root.left) + getLeafNodeCount2(root.right);
    }

    //第K层的节点的个数
    int getLeafNodeCount(TreeNode root,int k) {
        if (root == null) {
            return -1;
        }
        if (k == 1) {
            return 1;
        }
        return getLeafNodeCount(root.left,k-1) + getLeafNodeCount(root.right,k-1);
    }

    int getHeight(TreeNode root) {
        if (root == null) {
            return 0;
        }
        int leftH = getHeight(root.left);
        int reightH = getHeight(root.right);

        return leftH > reightH ? leftH+1 : reightH +1;
    }

    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, int val){
        if (root == null) {
            return null;
        }
        if (root.val == val) {
            return root;
        }
        TreeNode cur = find(root.left,val);
        if (cur != null) {
            return cur;
        }
        cur = find(root.right,val);
        if (cur != null) {
            return cur;
        }
        return null;
    }

    /*public List<Integer> preorderTraversal(TreeNode root) {
        List<Integer> list = new ArrayList<>();

    }*/


}